Mist lubrication consists of finely-dispersed atomized oil carried in an air stream. Migration lubrication consists of an air stream flowing through a conduit where, periodically, an oil droplet is injected into the conduit. The liquid oil droplet wets the inside wall of the conduit and thins to an oil film as it migrates along the wall to its destination. The purpose of both systems is to lubricate and cool machine elements such as ball bearings.
In machine assemblies employing spindle designs with multiple spaced bearings, where mist or migration lubricant is to be distributed to the bearings from a remote lubrication supply site, the usual practice is to drill very deep small-diameter holes within a machine housing to reach each bearing. These long small-diameter holes ar hard to machine, since a lone small-diameter drill tends to "walk" from its intended path. Additionally, in a great many cases, right-angle holes are also required to redirect lubricant toward the bearings from the long supply hole. Right-angled intersections can cause burrs which are hard to remove, and can cause the lubricant to reclassify and puddle, which results in unpredictable flow and improper distribution to bearings; these lubrication problems may cause failures in high speed bearing applications.